Internal combustion engine bearing and method of manufacturing internal combustion engine bearing

ABSTRACT

A semicircular tube-shaped bearing has a bearing main body that is formed from a resin, has a semicircular tube shape, and has an inner circumferential surface that slides over an opposing shaft and an outer circumferential surface that comes into contact with a housing. The semicircular tube-shaped bearing may have a structure in which multiple resin layers are laminated in a direction of radiation from the axial center. In this case, the bearing main body has a first layer that includes the outer circumferential surface and a second layer that includes the inner circumferential surface. The first layer is formed from a thermosetting resin. The first layer may include fiber reinforced resin in which fibers are mixed with a thermosetting resin. The second layer is formed from a thermoplastic resin. The second layer may include fiber reinforced resin in which fibers are mixed with a thermoplastic resin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/JP2016/065705, filed on May 27, 2016, which claimspriority to Japanese Application No. 2015-110790, filed on May 29, 2015.The entire disclosures of the above applications are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to a bearing for use in an internalcombustion engine of an automobile or the like.

BACKGROUND ART

A bearing that employs bimetal, which has a lining layer made of acopper-based or an aluminum-based bearing alloy on a metal backing madeof steel or the like, is known as a so-called main bearing or connectingrod bearing used in an internal combustion engine (engine) of anautomobile or the like (e.g., see JP 2013-167280). Also, although notfor use in an internal combustion engine, a bearing made of resin isknown as a bearing for use in office equipment or the like (e.g., see JP2008-19880 and JP 2000-87954).

One characteristic that is desired for an internal combustion engine inan automobile is an increase in the speed of rise in lubricanttemperature during cold starting, or in other words an improvement inthe so-called warm-up characteristic. However, when using a bearing madeof metal as described in JP 2013-167280, heat escapes from the lubricantvia the bearing due to the relatively high thermal conductivity thereof,and there has been a problem in that the temperature of the lubricantdoes not rise easily. The bearings described in JP 2008-19880 and JP2000-87954 are used in a non-lubricated environment such as in officeequipment, and have had the problem of not being able to be used asbearings for an internal combustion engine that are used along with alubricant.

In view of this, the present invention relates to technology forimproving mainly the warm-up characteristic with a bearing for aninternal combustion engine.

SUMMARY

The present invention provides an internal combustion engine bearingincluding: a bearing main body that is formed from a resin, has asemicircular tube shape, and has an inner circumferential surface thatis to slide over an opposing shaft and an outer circumferential surfacethat is to come into contact with a housing.

The bearing main body may include a layer formed from a thermosettingresin.

The bearing main body may include a layer formed from a thermoplasticresin.

The bearing main body may include a layer formed from a fiber reinforcedresin.

This internal combustion engine bearing may have a first layer that isformed from a thermosetting resin and includes the outer circumferentialsurface; and a second layer that is formed from a thermoplastic resinand includes the inner circumferential surface.

A thickness of the first layer may be greater than or equal to 80% of athickness of the bearing main body.

The bearing main body may have an oil passage between the first layerand the second layer.

The present invention also provides a method of manufacturing aninternal combustion engine bearing, including: producing a slurry bystirring a material that contains a resin in water; dehydrating theproduced slurry; and molding the dehydrated slurry by applying pressureand heat in a mold.

The present invention also provides a method of manufacturing aninternal combustion engine bearing, including: forming a first layerfrom a thermosetting resin; and forming a second layer by coating thefirst layer with a thermoplastic resin.

The present invention also provides a method of manufacturing aninternal combustion engine bearing, including: forming a first layer byinjecting a thermosetting resin into a first mold; arranging the formedfirst layer into a second mold; and forming a second layer by injectinga thermoplastic resin into the second mold in which the first layer isarranged.

The present invention also provides a method of manufacturing aninternal combustion engine bearing, including: forming a first layer byinjecting a thermosetting resin into a portion of an interior space of amold; and forming a second layer by injecting a thermoplastic resinbetween the mold and the first layer.

The present invention also provides a method of manufacturing aninternal combustion engine bearing, including: forming a first layer byusing a first male mold to press a thermosetting resin powder orgranules arranged in a female mold; and forming a second layer by usinga second male mold to press a thermoplastic resin powder or granulesarranged so as to be overlaid on the first layer formed in the femalemold.

ADVANTAGEOUS EFFECTS

According to the present invention, it is possible to improve thewarm-up characteristic with a bearing for an internal combustion engine.Also, it is possible to improve the mechanical strength compared to thecase where the internal combustion engine bearing is entirely made of athermoplastic resin, and it is possible to improve the slidingcharacteristic of the sliding surface that slides over the shaft incomparison with the case where the bearing is entirely made of athermosetting resin.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating crankshaft 1 in an internal combustionengine.

FIG. 2 is a diagram illustrating an external view of main bearing 10.

FIG. 3 is a diagram illustrating an external view of semicirculartube-shaped bearing 11.

FIGS. 4A and 4B are diagrams illustrating a cross-sectional structure ofsemicircular tube-shaped bearing 11.

FIG. 5 is a diagram illustrating a crush relief.

FIG. 6 is a diagram illustrating a cross-sectional structure of oilgroove 116 and oil hole 117.

FIG. 7 is a diagram illustrating fine grooves 118 formed in innercircumferential surface 112.

FIG. 8 is a conceptual diagram for describing a laminated structure of asemicircular tube-shaped bearing.

FIG. 9 is a diagram showing an external view of a bearing main body thathas an oil passage between a first layer and a second layer.

FIG. 10 is a cross-sectional diagram in which the bearing main body iscut along line X-X in FIG. 9.

FIG. 11 is a cross-sectional diagram in which the bearing main body iscut along line XI-XI in FIG. 10.

FIGS. 12A and 12B are flowcharts showing a bearing manufacturing methodaccording to a second example.

FIGS. 13A and 13B are diagrams illustrating manufacturing stepsaccording to the second example.

FIG. 14 is a flowchart showing a method of molding resin by sheetforming. FIGS. 15A-15C are flowcharts showing a method of molding abearing that has a laminated structure.

FIG. 16 is a flowchart showing a bearing manufacturing method accordingto a third example.

FIGS. 17A and 17B are diagrams illustrating manufacturing stepsaccording to the third example.

DETAILED DESCRIPTION 1. Structure

FIG. 1 is a diagram illustrating crankshaft 1 in an internal combustionengine. Crankshaft 1 includes main bearing 10, connecting rod bearing20, and crank washer 30. Main bearing 10 is a bearing that is attachedto the housing (not shown) of a cylinder block (not shown), grips ajournal of crankshaft 1, and supports crankshaft 1. Connecting rodbearing 20 is a bearing that is attached to connecting rod 2, grips apin of crankshaft 1, and supports connecting rod 2. Crank washer 30 is abearing that is used in combination with main bearing 10 and supportsforce in the axial direction of crankshaft 1. Crank washer 30 also has afunction of positioning crankshaft 1 and the cylinder block in the axialdirection.

FIG. 2 is a diagram illustrating an external view of main bearing 10.Main bearing 10 is constituted by two semicircular tube-shaped bearings(semicircular tube-shaped bearing 11 and semicircular tube-shapedbearing 12). Semicircular tube-shaped bearing 11 is a bearing (upperbearing) that is attached on the piston side in a view from crankshaft1, and semicircular tube-shaped bearing 12 is a bearing (lower bearing)that is attached on the opposite side. Semicircular tube-shaped bearing11 and semicircular tube-shaped bearing 12 are examples of an internalcombustion engine bearing according to the present invention.

FIG. 3 is a diagram illustrating an external view of semicirculartube-shaped bearing 11. Semicircular tube-shaped bearing 11 has bearingmain body 111. In this example, bearing main body 111 is entirely madeof a resin. A thermosetting resin or a thermoplastic resin is used asthe resin.

Examples of the thermosetting resin include thermosetting polyimideresin (PI), phenol resin (PF), urea resin (UF), melamine resin (MF),epoxy resin (EP), furan resin (FF), xylene resin (XF), alkyd resin (UP),silicone resin (SI), allyl resin (PDAP), and a material obtained bymixing fibers (glass fibers or carbon fibers) in these types of resin(so-called fiber-reinforced plastic (fiber reinforced resin), FRP).

Examples of the thermoplastic resin include polyvinyl chloride resin(PVC), polyvinylidene chloride resin (PVdC), polyvinyl alcohol resin(PVA), polystyrene resin (PS), acrylonitrile styrene resin (AS),acrylonitrile-butadiene-styrene resin (ABS), polyethylene resin (PE),ethylene vinyl acetate copolymer resin (EVA), polypropylene resin (PP),polyacetal resin (POM), polymethylmethacrylate resin (PMMA), modifiedacrylic resin (MS), cellulose acetate resin (CA), polycarbonate resin(PC), polyester resin (PET, PTT, PBT, PEN, PBN), polyamide resin (PA),polyurethane resin (PU), fluoric resin (PTFE, FEP, PFA, etc.),polyamide-imide resin (PAD, polyphenylene sulfide (PPS),polyetheretherketone (PEEK), thermoplastic polyimide (TPI),polybenzimidazole (PBI), polyetherimide resin (PEI), polysulfone resin(PSF), polyethersulfone resin (PES), and polyarylate resin (PAR).

Due to being used in an internal combustion engine, the heat resistanttemperature (e.g., continuous use temperature) of the resin ispreferable greater than or equal to 180° C., and more preferably greaterthan or equal to 200° C. Also, from the viewpoint of improving thewarm-up characteristic, the thermal conductivity of the resin ispreferably less than or equal to 1 W/mK, and more preferably less thanor equal to 0.5 W/mK. Also, in order to avoid adverse effects caused bymoisture absorption, such as change in dimensions, the moistureabsorption of the resin is preferably less than or equal to 0.2%. In thecase of thermoplastic resin in particular, there is a problem that theglass transition point decreases due to moisture absorption, andtherefore the moisture absorption is preferably less than or equal to0.2%. Furthermore, from the viewpoint of suppressing expansion in thecylinder block, the coefficient of linear expansion of the resin ispreferably less than or equal to 70×10⁻⁶.

Bearing main body 111 is entirely made of a resin, and thereforecompared to the case where the bearing main body is made of a metal,heat less easily escapes from the lubricant to the housing via thebearing, and it is possible to improve the speed of rise in thelubricant temperature when the engine is cold started.

Bearing main body 111 is molded with a semicircular tube shape, and hasinner circumferential surface 112 (sliding surface) that slides overcrankshaft 1, and outer circumferential surface 113 that is in contactwith the housing (not shown). The diameter φ of crankshaft 1 is 30 to150 mm for example, and bearing main body 111 has an inner diameter thatconforms to the diameter of crankshaft 1. Furthermore, bearing main body111 has mating surface 114 and mating surface 115 that are in contactwith semicircular tube-shaped bearing 12.

In this example, semicircular tube-shaped bearing 11 has oil groove 116in inner circumferential surface 112. Oil groove 116 is a groove forsupplying lubricant to the sliding surface and also holding suppliedlubricant. Also, oil groove 116 is provided with at least one oil hole117 that penetrates from outer circumferential surface 113 to innercircumferential surface 112. A portion of crankshaft 1 that is supportedby semicircular tube-shaped bearing 11 is provided with an oil hole (notshown) at a position opposing oil groove 116. This oil hole penetratesto a portion of crankshaft 1 that is supported by connecting rod bearing20. Lubricant is supplied to outer circumferential surface 113 ofsemicircular tube-shaped bearing 11 via an oil passage (not shown) thatis provided in the cylinder block. Lubricant that has been supplied toouter circumferential surface 113 is supplied to inner circumferentialsurface 112 (sliding surface) via oil hole 117, and lubricates the mainbearing. The lubricant on the sliding surface is supplied to the slidingsurface of connecting rod bearing 20 via the oil hole of crankshaft 1.

FIG. 4 is a diagram illustrating the cross-sectional structure ofsemicircular tube-shaped bearing 11. FIG. 4(A) is an external view ofsemicircular tube-shaped bearing 11 seen from a direction perpendicularto the mating surfaces. FIG. 4(B) is a cross-sectional view taken alongB-B in FIG. 4(A). This cross-section is a cross-section that isperpendicular to the axial direction (a cross-section that is parallelto the sliding direction). In this example, in this cross-section, thewall thickness of bearing main body 111 is not uniform, but ratherincreases in thickness toward the central portion, and decreases inthickness from the central portion toward the end portions (matingsurfaces). This configuration is employed such that the center of theinner diameter circle (circle described by inner circumferential surface112) is eccentric (shifted) outward from the center of the outerdiameter circle (circle described by outer circumferential surface 113).A so-called oil relief is formed by this eccentricity. Oil relief refersto the gap between the inner circumferential surface and a circle basedon the central portion of the inner circumferential surface of thesemicircular tube-shaped bearing (a circle that passes through thecentral portion of the inner circumferential surface). The depth(amount) of the oil relief is measured based on a predetermined height(e.g., 6 to 13 mm) from the mating surfaces, and is 0.005 to 0.025 mmfor example. The oil relief expands the oil clearance in the vicinity ofthe mating surfaces, and aids the formation of wedge film pressure.Also, the oil relief furthermore aids the formation of an oil film, andcools the bearing by increasing the amount of oil.

Also, in this example, oil groove 116 is formed so as to extend theentire length in the sliding direction, from mating surface 114 tomating surface 115.

The depth of the oil groove is also not uniform, but rather increases indepth toward the central portion of bearing main body 111, and decreasesin depth from the central portion toward the mating surfaces.

Furthermore, bearing main body 111 is provided with a crush relief.Crush relief refers to a “relief” provided over the entire width ofbearing main body 111 in portions of inner circumferential surface 112that are adjacent to mating surface 114 and mating surface 115.

FIG. 5 is a diagram illustrating a crush relief. Note that in order tofacilitate the description, the crush relief is illustrated in anexaggerated manner compared to an actual crush relief. Depth d of thecrush relief is the difference between the position of innercircumferential surface 112 and a circle described by the portion ofinner circumferential surface 112 other than the crush relief at theposition of the mating surface, and length L of the crush relief is thelength of the portion of inner circumferential surface 112 in which thecrush relief is formed. Depth d of the crush relief is 0.01 to 0.06 mmfor example, and length L of the crush relief is 4 to 9.5 mm forexample. When the bearing is attached to the housing, even if a portionof inner circumferential surface 112 in the vicinity of a mating surfacefalls slightly toward the opposing shaft, the crush relief preventscontact with the shaft. The crush relief also has an effect of coolingthe bearing by discharging lubricant in the vicinity of the matingsurfaces, and an effect of discharging foreign matter that haspenetrated to the sliding surface.

FIG. 6 is a diagram illustrating the cross-sectional structure of oilgroove 116 and oil hole 117. FIG. 6 shows a cross-section that isperpendicular to the sliding direction (a cross-section that is parallelto the axial direction). In this cross-section, oil groove 116 has atrapezoid shape in which the bottom portion is narrower and the openingportion is wider. Bottom width W of oil groove 116 is 2 to 5 mm forexample, and depth d of oil groove 116 is smaller than bottom width W,such as 0.5 to 1 mm.

In this example, fine grooves (microgrooves) that are finer than oilgroove 116 are formed in a portion of inner circumferential surface 112other than oil groove 116.

FIG. 7 is a diagram illustrating fine grooves 118 formed in innercircumferential surface 112. Fine grooves 118 are grooves that have acircular arc-shaped cross-section and are arranged regularly. In thisexample, the apex between two adjacent grooves has a sharp shape ratherthan being flat. The gap between two adjacent apexes is referred to aspitch P, and the depth of the grooves based on the apex is referred toas depth h. Pitch P of fine grooves 118 is larger than depth h thereof.Depth h is preferably 1 to 20 μm, and more preferably 1 to 6 μm, forexample. Pitch P is preferably 0.1 to 0.4 mm, and more preferably 0.1 to0.2 mm, for example. Fine grooves 118 shorten the time required to movefrom a non-lubrication state to a fluid lubrication state in a so-calledStribeck chart, thus ensuring early arrival of the fluid lubricationstate and improving conformability and oil retainability.

Also, bearing main body 111 has interference (so-called crush). In otherwords, bearing main body 111 has a longer diameter than a semicircle.

The description will now return to FIG. 3. Semicircular tube-shapedbearing 11 has claw 119 on outer circumferential surface 113. Claw 119is an example of a rotation prevention protrusion portion forsuppressing rotation of semicircular tube-shaped bearing 11 relative tothe housing. Furthermore, claw 119 has functions of preventing erroneousattachment and performing positioning in the circumferential directionand the axial direction.

Also, semicircular tube-shaped bearing 11 has so-called bulge. Bulgerefers to setting the outer diameter dimension larger than the innerdiameter of the housing in the free state (not attached to the housing)in a view from the axial direction. This bulge is 0.8 to 1.3 mm forexample. Bulge has an effect of allowing the outer circumference ofsemicircular tube-shaped bearing 11 to conform to the innercircumference of the housing during attaching, and has an effect ofpreventing semicircular tube-shaped bearing 11 from moving away from orfalling out of the housing during attachment.

A detailed description will not be given for semicircular tube-shapedbearing 12, which is the same as semicircular tube-shaped bearing 11with the exception of not having an oil groove or an oil hole. Adetailed description will not be given for connecting rod bearing 20either, which is the same as main bearing 10 in that two semicirculartube-shaped bearings are used in a combined state. It should be notedthat in connecting rod bearing 20, neither of the semicirculartube-shaped bearings has an oil groove or an oil hole. The twosemicircular tube-shaped bearings of connecting rod bearing 20 are otherexamples of an internal combustion engine bearing according to thepresent invention.

Also, semicircular tube-shaped bearing 11 and semicircular tube-shapedbearing 12 may have a structure in which multiple resin layers arelaminated in a direction of radiation from the axial center. FIG. 8 is aconceptual diagram for describing the laminated structure ofsemicircular tube-shaped bearing 11. Oil groove 116 and oil hole 117 arenot shown in FIG. 8. Note that the laminated structure of semicirculartube-shaped bearing 11 shown in FIG. 8 applies to semicirculartube-shaped bearing 12 as well.

As shown in FIG. 8, bearing main body 111 has first layer 1111 thatincludes outer circumferential surface 113, and second layer 1112 thatincludes inner circumferential surface 112. First layer 1111 is formedfrom any of the above-described thermosetting resins. Also, first layer1111 may include fiber reinforced resin in which fibers are mixed withany of the above-described thermosetting resins. Second layer 1112 isformed from any of the above-described thermoplastic resins. Also,second layer 1112 may include fiber reinforced resin in which fibers aremixed with any of the above-described thermoplastic resins.

Note that thickness t1 of first layer 1111 is desirably greater than orequal to 80% of thickness t of bearing main body 111. Accordingly, thereis an improved possibility that bearing main body 111 withstands loadreceived from crankshaft 1 or the like. Also, instead of a two-layerstructure including first layer 1111 and second layer 1112, bearing mainbody 111 may include three or more resin layers that are laminated.

Also, bearing main body 111 may have oil passage 116 a between layers.FIG. 9 is a diagram showing an external view of bearing main body 111that has oil passage 116 a between first layer 1111 and second layer1112. FIG. 10 is a cross-sectional diagram in which bearing main body111 is cut along line X-X in FIG. 9. FIG. 11 is a cross-sectionaldiagram in which bearing main body 111 is cut along line XI-XI in FIG.10.

As shown in FIG. 10, bearing main body 111 has a structure in whichfirst layer 1111 and second layer 1112 are laminated, and oil passage116 a is provided between first layer 1111 and second layer 1112 in thecenter in the width direction (the extending direction of crankshaft 1instructed by bearing main body 111). This oil passage 116 a is providedwith one or more oil holes 117 b that penetrate from outercircumferential surface 113 to first layer 1111. Also, one or more oilholes 117 a are formed penetrating from oil passage 116 a to secondlayer 1112 toward inner circumferential surface 112.

Accordingly, lubricant supplied from an oil passage (not shown) providedin the cylinder block passes through oil holes 117 b from outercircumferential surface 113 side, fills oil passage 116 a, and thenpasses through oil holes 117 a and reaches inner circumferential surface112. Accordingly, sliding surfaces of crankshaft 1 and bearing main body111 (inner circumferential surface 112) slide over each other.

Note that the positions of oil holes 117 a and oil holes 117 b maymatch, but are not required to match, as shown in FIG. 11 for example.As shown in FIG. 1, even if oil holes 117 b are not provided onextension lines of oil holes 117 a, lubricant supplied from oil holes117 b passes through oil passage 116 a and oil holes 117 a, and issupplied to inner circumferential surface 112.

2. Manufacturing Method

Several methods can be applied as methods for manufacturing main bearing10 and connecting rod bearing 20.

2-1. First Example

In this example, bearings are molded one at a time by injection molding,compression molding, or the like. The oil groove, oil holes, and finegrooves may be molded by forming an oil groove, oil holes, and finegrooves in the mold in advance, or may be formed by performing cuttingor the like after molding into the semicircular tube shape.

2-2. Second Example

FIG. 12 is a flowchart showing a bearing manufacturing method accordingto a second example, and FIG. 13 is a diagram illustrating manufacturingsteps.

In step S11 shown in FIG. 12(A), resin is molded into a semicirculartube shape. FIG. 13(A) illustrates a resin molded body that is obtainedin step S11. The semicircular tube shape referred to here is a shape inwhich the length in the axial direction is longer than the width of thecompleted bearing. This molding is performed by injection molding,compression molding, or the like.

In step S12 in FIG. 12(A), molded bodies having the width of thecompleted bearing are cut from the resin molded body. FIG. 13(B)illustrates the cut molded bodies.

In step S13 shown in FIG. 12(A), necessary finishing processing and thelike are carried out on the molded bodies. The finishing processingreferred to here includes oil groove formation, oil hole formation, finegroove formation, and chamfering, for example.

Note that if resin is molded into a semicircular tube shape with thewidth of the completed bearing in step S11, step S12 shown in FIG. 12(A)may be omitted. The flowchart shown in FIG. 12(B) shows the bearingmanufacturing method in this case. Here, in the case of performing resininjection molding for example, if a mold with an interior space designedwith the size of the completed bearing is used, the cutting performedafter molding may be omitted.

Also, besides injection molding and compression molding, the molding instep S11 may be sheet forming. Here, “sheet forming” is a solid membermanufacturing method that has a step in which a material containingresin is stirred in water to produce a slurry, a step in which theproduced slurry is dehydrated, and a step in which the dehydrated slurryis molded by being pressed and heated in a mold.

FIG. 14 is a flowchart showing a method of molding resin by sheetforming. In step S101 shown in FIG. 14, a material containing resin isprepared as a compound. This material contains a thermosetting resin ora thermoplastic resin, as well as glass fibers, carbon fibers, inorganicfibers, an inorganic filler, a friction adjusting material, or the like.

In step S102, the above-described material is introduced into water andstirred or mixed to produce a slurry.

In step S103, the above-described slurry is supplied to a filter anddehydrated. Suction filtration, pressure filtration, or the like isapplied as dehydration.

In step S104, the above-described dehydrated slurry is supplied to amold and then pressed and heated, thus being molded into a predeterminedshape, such as a semicircular tube shape.

When the resin molded body is molded by the sheet forming steps of stepS101 to step S104 shown in FIG. 14, the material is more readilydistributed evenly than in the case where another process is applied.Also, in the case where the material contains fibers, the fibers are notlikely to be aligned in a specific direction, thus making it possible togive isotropy to the strength of the resin molded body, and to improvethe strength.

Also, in the case where the bearing has a laminated structure as shownin FIG. 8 described above, various methods can be employed for themolding of step S11. FIG. 15 is a flowchart showing a method of moldinga bearing that has a laminated structure.

A bearing having a laminated structure may be molded by performingcoating as shown in FIG. 15(A) for example. In step S201 in FIG. 15(A),a first layer is molded from a thermosetting resin material usinginjection molding, compression molding, sheet forming, or the like.Then, in step S202, a second layer is molded by coating the surface ofthe first layer with a thermoplastic resin.

Also, a bearing that has a laminated structure may be molded byinjection molding multiple resin pieces at different times as shown inFIG. 15(B) for example. In step S301 in FIG. 15(B), thermosetting resinis injected into one portion of the interior space of a mold.Accordingly, a first layer that includes outer circumferential surface113 is formed. Then, in step S302, thermoplastic resin is injectedbetween the mold and the first layer. Accordingly, the thermoplasticresin fills a portion not occupied by the first layer in the interiorspace of the mold, and a second layer is formed. This second layerincludes inner circumferential surface 112.

Also, a bearing having a laminated structure may be molded by so-calledmulticolor molding as shown in FIG. 15(C) for example. Multicolormolding is a method in which resin molded bodies are switched betweenmultiple molds, a resin molded body is molded at a prior stage, and thenanother type of resin is injected between the resin molded body and anew mold to manufacture a molded body that is constituted by multipletypes of resin layers.

In step S401 in FIG. 15(C), thermosetting resin is injected into a firstmold. Accordingly, a first layer that includes outer circumferentialsurface 113 is formed. Then, in step S402, the above-described firstlayer is moved to and arranged in a second mold. The interior space ofthe second mold is designed to be larger than the interior space of thefirst mold. Furthermore, in step S403, thermoplastic resin is injectedinto the second mold. Accordingly, the thermoplastic resin fills aportion not occupied by the first layer in the interior space of thesecond mold, and a second layer is formed. This second layer includesinner circumferential surface 112.

This multicolor molding is applicable to compression molding as well. Inthis case, step S402 described above can be omitted.

For example, in step S401 of FIG. 15(C), a thermosetting resin powder orgranules are introduced through an opening of a female mold, and then afirst male mold is inserted into the opening of the female mold, and theresin is pressed. At this time, the resin may be pre-heated, and mayhave been subjected to degassing processing. Accordingly, the pressedthermosetting resin hardens inside the interior space of the femalemold, and a first layer that includes outer circumferential surface 113is formed. The first male mold constitutes a first mold along with thefemale mold.

The first male mold is removed, and then in step S403, a thermoplasticresin powder or granules are introduced through the opening of theabove-described female mold. The introduced thermoplastic resin isarranged so as to be overlaid on the first layer in the interior spaceof the female mold. A second male mold is then inserted into the openingof the female mold, and the resin is pressed. Accordingly, thethermoplastic resin hardens in the space between the first layer and thesecond male mold, and a second layer is formed. This second layerincludes inner circumferential surface 112. The second male moldconstitutes a second mold along with the female mold.

Note that the second male mold may be different from or the same as thefirst male mold. Also, the order in which the thermosetting resin andthe thermoplastic resin are introduced may be reversed. Moreover, theresin that is molded in the latter stage may be introduced before theresin molded in the earlier stage has completely hardened.

2-3. Third Example

FIG. 16 is a flowchart showing a bearing manufacturing method accordingto a third example, and FIG. 17 is a diagram illustrating manufacturingsteps.

In step S21, resin is molded into a circular tube shape. FIG. 17(A)illustrates a resin molded body that is obtained in step S21. Thecircular tube shape referred to here is a shape in which the length inthe axial direction is longer than the width of the completed bearing.This molding is performed by injection molding, compression molding, orthe like.

In step S22, the circular tube-shaped resin molded body is bisected byperforming cutting in the axial direction. Two semicircular tube-shapedresin molded bodies are obtained. FIG. 17(B) illustrates resin moldedbodies that are obtained in step S22. Thereafter, the step in which amolded body having the width of the completed bearing is cut from thesemicircular tube-shaped resin molded body (step S23) and the finishingprocessing (step S24) are similar to steps S12 and S13.

Note that similarly to the second example described above, if resin ismolded into a circular tube shape having the width of the completedbearing in step S21 in FIG. 16, step S23 shown in FIG. 16 may beomitted.

Also, the molding in step S21 of FIG. 16 may be performed by sheetforming, similarly to the second example.

Also, in the case where the bearing is to have a laminated structure,similarly to the second example, various methods can be applied to themolding in step S21 of FIG. 16, such as coating, injection molding atdifferent times, and multicolor molding.

3. Variations

The present invention is not limited to the embodiment described above,and various modifications can be carried out. The following describesseveral variations. Two or more of the following variations may be usedin combination.

The specific shape of the bearing is not limited to the shapeillustrated in the embodiment. For example, at least one of the oilgroove, the oil holes, the fine grooves, the oil relief, the crushrelief, and the claw may be omitted. Alternatively, at least one of anoil groove and oil holes may be provided in semicircular tube-shapedbearing 12 and connecting rod bearing 20. Also, the specific sizes ofthese elements are not limited to the sizes illustrated in theembodiment. Moreover, the specific shapes, number of, and positions ofthe oil groove and the oil holes are not limited to those illustrated inthe embodiment. Furthermore, the semicircular tube-shaped bearing is notrequired to have a bulge.

In the embodiment, an example is described in which oil groove 116extends from mating surface 114 to mating surface 115. However, the oilgroove may be formed in only a portion in the circumferential direction.Also, the oil groove is not limited to being formed in the slidingsurface (inner circumferential surface), and may be formed in the outercircumferential surface. In other words, it is sufficient that the oilgroove is formed in at least one of the inner circumferential surfaceand the outer circumferential surface of the bearing main body.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. An internalcombustion engine bearing comprising: a bearing main body that is formedfrom a resin, has a semicircular tube shape, and has an innercircumferential surface that is to slide over an opposing shaft and anouter circumferential surface that is to come into contact with ahousing, wherein the bearing main body includes a first layer that isformed from a thermosetting resin and includes the outer circumferentialsurface; and a second layer that is formed from a thermoplastic resinand includes the inner circumferential surface.
 6. The internalcombustion engine bearing according to claim 5, wherein a thickness ofthe first layer is greater than or equal to 80% of a thickness of thebearing main body.
 7. The internal combustion engine bearing accordingto claim 5, wherein the bearing main body has an oil passage between thefirst layer and the second layer.
 8. A method of manufacturing aninternal combustion engine bearing, comprising: producing a slurry bystirring a material that contains a resin in water; dehydrating theproduced slurry; and molding the dehydrated slurry by applying pressureand heat in a mold.
 9. A method of manufacturing an internal combustionengine bearing, comprising: forming a first layer from a thermosettingresin; and forming a second layer by coating the first layer with athermoplastic resin.
 10. A method of manufacturing an internalcombustion engine bearing, comprising: forming a first layer byinjecting a thermosetting resin into a first mold; arranging the formedfirst layer into a second mold; and forming a second layer by injectinga thermoplastic resin into the second mold in which the first layer isarranged.
 11. A method of manufacturing an internal combustion enginebearing, comprising: forming a first layer by injecting a thermosettingresin into a portion of an interior space of a mold; and forming asecond layer by injecting a thermoplastic resin between the mold and thefirst layer.
 12. A method of manufacturing an internal combustion enginebearing, comprising: forming a first layer by using a first male mold topress a thermosetting resin powder or granules arranged in a femalemold; and forming a second layer by using a second male mold to press athermoplastic resin powder or granules arranged so as to be overlaid onthe first layer formed in the female mold.
 13. The internal combustionengine bearing according to claim 6, wherein the bearing main body hasan oil passage between the first layer and the second layer.